Plastic bearing, particularly for use in MacPherson strut

ABSTRACT

A MacPherson strut tube having an upper spring seat, a spring, a strut tube, and a ring bearing disposed for engaging the spring seat, the spring and the strut tube. The ring bearing comprises an upper casing, a lower casing, and a plastic ring engaged between the upper and lower casings, thereby forming said ring bearing.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims priority of U.S.provisional application serial No. 60/435,978, filed Dec. 20, 2002, thedisclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to a ring bearing for use in a MacPhersonstrut, and more particularly to a ring bearing made of plastic.

[0004] 2. Background Art

[0005] As shown in FIG. 1, a MacPherson strut assembly has a strut tube5, and a lower spring seat 4 welded to the strut tube 5. A spring 6 ispositioned directly on the spring support 4, or may be seated in arubber dampener which is positioned on the spring seat 4. The latterreduces the road vibration transmitted from the wheels. The upper end ofthe spring 6 is held by the upper spring seat 1 which can also utilize arubber dampening medium 3. A bearing 2 is captured in the upper springseat 1 and keeps the upper seat 1 concentric to the strut tube 5. Theupper seat 1 is interference fitted into the bore of the bearing 2.

[0006] An example of a known bearing 2 is described in detail inconnection with FIG. 2. It supports the loads which are transferredthrough the spring 4 in a dual path arrangement and supports the loadsfrom the spring 4 and strut tube 5 in a single path system.

[0007] The bearing 2 (FIG. 2) comprises upper and lower plastic casings8 and 9. The arm extensions 8 a, 8 b, 8 c, 8 d, 9 a, 9 b provide asealing function and on one side (8 d) a locking feature. A set of balls10 ride on two hardened steel raceways 11 a 11 b. The raceways may beshaped corresponding to the curvature of the balls 10, or may be stampedin approximately a Gothic arch shape, for example. The latter shapeprovides for axial and radial load-carrying capacity. It also eliminatesside movement in the bearing, which eliminates the fouling of the upperand lower plastic casings.

[0008] Another known bearing 2 a (FIG. 3) is comprised of an upperhardened steel raceway 12 which is stamped to form an angular contactbearing 2 a. A set of balls 10 are held by a lower hardened steelraceway 13 which is covered partially in rubber 14. The rubber 14provides a sealing function on the inner and outer surfaces. An innerlip 15 of the lower raceway 13 seats into a groove 16 in the upperraceway 12. This locks the bearing 2 a together.

[0009] As described above, the known designs utilize steel balls inassociated steel raceways. The raceways and balls are held in place andprotected from contamination by upper and lower plastic casings, whichlock together by the use of angled lips or extensions which can be onboth the outer and inner portions of the upper and lower casings.

[0010] Despite the general success of these designs, there is acontinuing need to reduce the manufacturing cost of the bearing and theweight of the bearing assembly, without altering its overall size.

SUMMARY OF THE INVENTION

[0011] According to several forms of the invention shown herein, abearing comprises a plastic chain with elongated sections forming theload-carrying members. The links between the sections are reduced incross-section and allow for limited bending when the load is applied inuse.

[0012] In one embodiment of the invention, the sections are designed tocarry a pure axial load which is perpendicular to the bearing topsurface. The bearing provides a point contact as seen in cross-section.The bearing surfaces of the upper and lower casings are preferablymirror images of each other.

[0013] The sections are profiled to permit the carrying of grease tolubricate the sliding surfaces during operation.

[0014] The weight of the bearing is reduced while maintaining thefitting diameters prescribed by the mating components. The rollingaction of the balls is replaced by a sliding action, which mayadvantageously be between two dissimilar plastic chemistries.

[0015] In a second embodiment, the sections are designed to carry theload over a defined angle. The bearing operates as an arc-contactbearing. This bearing reduces sideways travel of the casings andpossibly squeaking and vibration.

[0016] According to a third embodiment, further improvement is obtainedwith a four-arc contact bearing.

[0017] In a fourth embodiment, the sections are designed to carry theload over a defined angle. This bearing operates as a combination of aline-contact bearing and an arc-contact bearing.

[0018] A fifth embodiment is designed to carry the load over a definedangle and operates as a four-point contact bearing.

[0019] A sixth embodiment is designed to carry the load over a definedangle and operates as a taper-line-contact bearing.

[0020] Other features and advantages of the present invention willbecome apparent from the following description of several embodiments ofthe invention which refers to the accompanying drawings.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION FirstEmbodiment—Point Contact Bearing

[0021] The bearing 15 is depicted in FIGS. 4 and 5. It may have the samestrut bearing upper casing 8 (plastic cap) and lower casing 9 (plasticbase) as in FIGS. 1-2. The prior art steel raceways 11 a 11 b androlling elements 10 have been replaced by a plastic ring 20. The ring 20is profiled to establish a point contact bearing which is capable ofsupporting axial load. The upper and lower casings 8 and 9 and theplastic ring 20 each have a single radius. The radius of the upper andlower casings is R₂ while the radius of the ring 20 is R₁, whereinR₁<R₂.

[0022] The ring also may have radial grooves in its top and bottomsurfaces as seen for example in FIGS. 12-14, which would eliminatecontact at the central point where the ring 20 meets the upper and lowercasings. This would reduce the friction of the assembly.

[0023] The ring also may have recesses in its top and bottom sides againas seen for example in FIGS. 12-14, which are used to carry lubrication.The lubrication reduces friction and aids in the sealing of the bearingfor improved lifetime. The design is economical due to the eliminationof steel raceways and balls.

[0024] The design is economical due to the elimination of steel racewaysand balls. The radius of the plastic ring of the upper/lower casing(i.e. R₁ and R₂) can be adjusted according to the required loadcapacity. The weight of the bearing is reduced while maintaining thefitting diameters prescribed by the mating components. The rollingaction of the balls is replaced by a sliding action which may be betweentwo dissimilar plastic chemistries. The retained lubricant suppliessealing and continued lubrication through the life of the bearing.

Second Embodiment—Arc-Contact Bearing

[0025] The second embodiment of a bearing 25 is depicted in FIGS. 6 and7, FIG. 6 being a partly broken-away perspective view and FIG. 7 being apartial cross-section. It has the same strut bearing upper casing(plastic cap) 8 and lower casing (plastic base) 9 as in FIGS. 4-5. Theprior art steel raceways and rolling elements have been replaced by aplastic ring 30. Said ring 30 is profiled to establish an arc-contactbearing which is capable of supporting radial and axial loads. A contactinterface of single radius R is formed between the upper and lowercasings and the plastic ring 30.

[0026] The ring may have central radial grooves at its top and bottomsurfaces as seen for example in FIGS. 12-14 to eliminate contact wherethe ring meets the arches of the upper and lower casings. This featurewould keep the friction of the assembly low.

[0027] The ring 30 also has recesses 32, 34 on its top and bottom sideswhich are used to carry lubrication. Said lubrication reduces frictionand aids in the sealing of the bearing for improved lifetime.

[0028] An economical design is achieved due to the elimination of steelraceways and balls. The prior art weight of the bearing is reduced whilemaintaining the fitting diameters prescribed by the mating components.The rolling action of the balls is replaced by a sliding action, whichmay be between two dissimilar plastic chemistries. The retainedlubricant supplies sealing and continued lubrication through the life ofthe bearing.

Third Embodiment

[0029] Another arc-contact bearing 35 is depicted in FIGS. 8 and 9. Ithas the same strut bearing upper casing (plastic cap) 8 and lower casing(plastic base) 9 as in FIGS. 4-5. The prior art steel raceways androlling elements have been replaced by a plastic ring 40. Said ring isprofiled to establish a four-arc contact bearing which is capable ofsupporting radial and axial loads. Contact between the ring 40 and theupper and lower casings 8 and 9 is provided by both the ring and thecasings having a single radius R₁, over an angular range defined byα<contact angle<β.

[0030] The ring 40 also has flattened top and bottom surfaces, leavingspaces between the top and bottom of the ring and the upper and lowercasings. The ring also may have radial grooves in its top and bottomsurfaces as seen for example in FIGS. 12-14. These arrangementseliminate central contact where the ring meets the upper and lowercasings, keeping the friction of the assembly low.

[0031] The ring also has recesses on its top and bottom sides, again asseen for example in FIGS. 12-14, which are used to carry lubrication.Said lubrication reduces friction and aids in the sealing of the bearingfor improved lifetime.

[0032] The design is economical achieved due to the elimination of steelraceways and balls. The parameters (i.e. R₁, R₂, R₃, α and β ) can beadjusted to achieve the required axial and radial load capacity. Theweight of the bearing is reduced while maintaining the fitting diametersprescribed by the mating components. The rolling action of the balls isreplaced by a sliding action, which may be between two dissimilarplastic chemistries. The retained lubricant supplies sealing andcontinued lubrication through the life of the bearing.

Fourth Embodiment—Line/Arc Contact Bearing

[0033] The fourth bearing 45 is depicted in FIGS. 10 and 11. It has astrut bearing upper casing (plastic cap) 8 a and lower casing (plasticbase) 9 a similar to those in FIGS. 4-5, with modifications as follows.The prior art steel raceways and rolling elements have been replaced bya plastic ring 50. Said ring 50 is profiled to establish a line/arccontact bearing which is capable of supporting radial and axial loads.The contact is provided by the casings 8 a and 9 a and the ring 50having a single radius R, over an angular range defined by α<contactangle<β.

[0034] The ring also has radial grooves 52, 54 at its top and bottomsurfaces to eliminate the possibility of contact in the center regionsof the upper and lower casings 8 a, 9 a. This will keep the friction ofthe assembly low.

[0035] The upper and lower casings 8 a, 9 a have respective projections56, 58 which project into the grooves 52, 54, respectively.

[0036] The ring also has recesses on its top and bottom sides as shownfor example in FIGS. 12-14 which are used to carry lubrication. Saidlubrication reduces friction and aids in the sealing of the bearing forimproved lifetime.

[0037] The design is economical due to the elimination of steel racewaysand balls. The parameters (i.e. R, α and β) can be adjusted in responseto the desired axial and radial load capacity. The weight of the bearingis reduced while maintaining the fitting diameters prescribed by themating components. The rolling action of the balls is replaced by asliding action, which may be between two dissimilar plastic chemistries.The retained lubricant supplies sealing and continued lubricationthrough the life of the bearing.

Fifth Embodiment—Bearing with Spring Seat

[0038] A fifth bearing 55 is shown in FIGS. 12-14. As shown in FIG. 12,the bearing itself is shown fitted into a representative upper springseat 1 a corresponding to the upper spring seat 1 shown in FIG. 1. It isretained in the seat 1 a by the use of plastic ears 56 on the lowerbearing casing 9 b which are snapped under rubber tabs 57 on thevulcanized steel spring seat 1 a.

[0039] In FIG. 13, the bearing 55 is depicted in cross-section. FIG. 14is a partly broken-away perspective view. It has a strut bearing uppercasing or plastic cap 8 similar to that in FIGS. 4-5. The lower sectionor plastic base 9 b is similar to that in FIGS. 4-5, with modificationsas described above.

[0040] The prior art steel raceways and rolling elements have beenreplaced by a plastic ring 60. Said ring 60 is profiled to establish afour-point contact bearing at its top and bottom, inner and outercorners which is capable of supporting radial and axial loads. The ringalso has central grooves 62, 64 formed in its top and bottom surfaces toeliminate contact where the ring 60 meets the upper and lower casings 8,9 b. This reduces the friction of the assembly.

[0041] The ring also has recesses 66, 68 on its top and bottom sideswhich are used to carry lubrication. Said lubrication reduces frictionand aids in the sealing of the bearing for improved lifetime.

[0042] The weight of the bearing is reduced while maintaining thefitting diameters prescribed by the mating components. The rollingaction of the balls is replaced by a sliding action, which may bebetween two dissimilar plastic chemistries. The retained lubricantsupplies sealing and continued lubrication through the life of thebearing.

Sixth Embodiment

[0043] A sixth bearing is depicted in FIGS. 15 and 16. It has a strutbearing upper casing (plastic cap) 8 c and lower casing (plastic base) 9c. The prior art steel raceways and rolling elements have been replacedby a plastic ring 70. Said ring 70 is generally V-shaped incross-section and is profiled to establish a multiple-point contactbearing which is capable of supporting axial load. The upper, lowercasings 8 c, 9 c and plastic ring 70 have substantially flat interfaces71, 72, 73, 74 at their upper and lower, inner and outer regions. A flatcentral face 75 is formed on the top surface of the ring 70, forming anangle α with the interface 71 and an angle 180°-α with the interface 73.A flat central face 76 is formed on the upper surface of the lowercasing 9 c, forming an angle β with the interface 74 and an angle 180°-βwith the interface 72. The flat surfaces 75, 76 form gaps between thering 70 and the top and bottom casings 8 c, 9 c to eliminate contact atthe central portions where the ring and the upper and lower casingsmeet. This will keep the friction of the assembly low.

[0044] Additional recessess 77 are formed in other respective surfacesof the ring 70 which carry lubrication and further reduce friction.

[0045] The ring also has recesses on its top and bottom sides as seenfor example in FIGS. 12-14 which are used to carry lubrication. Saidlubrication reduces friction and aids in the sealing of the bearing forimproved lifetime.

[0046] The design is economical due to the elimination of steel racewaysand balls. The design parameters, i.e. α and β, can be modified toimprove axial and radial load capacity. α may be greater than β as shownin FIG. 16, or α and β may have another relationship.

[0047] The weight of the bearing is reduced while maintaining thefitting lines prescribed by the mating components. The rolling action ofthe balls is replaced by a sliding action, which may be between twodissimilar plastic chemistries. The retained lubricant supplies sealingand continued lubrication through the life of the

[0048] Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art.Therefore, the present invention is not limited by the specificdisclosure herein.

What is claimed is
 1. A MacPherson strut having an upper spring seat, aspring, a strut tube, and a ring bearing disposed for engaging thespring seat, the spring and the strut tube; wherein the ring bearingcomprises: an upper casing; a lower casing; and a plastic ring engagedbetween the upper and lower casings, thereby forming said ring bearing.2. The MacPherson strut of claim 1, wherein the upper and lower casingsare made of plastic.
 3. The MacPherson strut of claim 2, wherein saidplastic ring is made of a different plastic material from that of saidupper and lower plastic casings.
 4. The MacPherson strut of claim 1,further comprising sealing and locking elements on the upper and lowercasings.
 5. The MacPherson strut of claim 1, wherein said plastic ringhas portions of reduced cross-sectional area which increase theflexibility of said plastic ring.
 6. The MacPherson strut of claim 1,wherein said plastic ring has central grooves in its upper and lowersurfaces which reduce contact friction with the respective centralfacing surfaces of the upper and lower casings.
 7. The MacPherson strutof claim 6, further comprising additional grooves or recesses in theupper and/or lower surfaces of the plastic ring which further reducecontact friction with the respective facing surfaces of the upper andlower casings.
 8. The MacPherson strut of claim 1, wherein said plasticring has lateral grooves or recesses capable of holding lubrication. 9.The MacPherson strut of claim 1, wherein upper and lower facing surfacesof said plastic ring respectively engage said upper and lower casings atcorresponding lower and upper facing surfaces thereof.
 10. TheMacPherson strut of claim 9, wherein said respective facing surfaces ofsaid casings and said ring are engaged primarily at central portionsthereof.
 11. The MacPherson strut of claim 10, wherein said respectivefacing surfaces are curved, said facing surfaces of said ring having atleast in part a smaller radius of curvature than said facing surfaces ofsaid casings.
 12. The MacPherson strut of claim 10, wherein saidrespective facing surfaces are curved, said facing surfaces of said ringhaving at least in part the same radius of curvature as said facingsurfaces of said casings.
 13. The MacPherson strut of claim 9, whereinsaid respective facing surfaces of said casings and said ring areengaged primarily at inner and outer portions thereof.
 14. TheMacPherson strut of claim 13, wherein central portions of said facingsurfaces of said plastic ring are spaced away from the correspondingfacing surfaces of the upper and lower casings.
 15. The MacPherson strutof claim 13, wherein said inner and outer portions of said ring and saidcasings are at least partially curved with the same radius of curvature.16. The MacPherson strut of claim 9, wherein said respective facingsurfaces of said ring and said upper and lower casings are at leastpartially flat.
 17. A ring bearing, comprising: an upper casing; a lowercasing; and a plastic ring engaged between the upper and lower casings,thereby forming said ring bearing.
 18. The ring bearing of claim 17,wherein the upper and lower casings are made of plastic.
 19. The ringbearing of claim 18, wherein said plastic ring is made of a differentplastic material from that of said upper and lower plastic casings. 20.The ring bearing of claim 17, further comprising sealing and lockingelement on the upper and lower casings.
 21. The ring bearing of claim17, wherein said plastic ring has portions of reduced cross-sectionalarea which increase the flexibility of said plastic ring.
 22. The ringbearing of claim 17, wherein said plastic ring has central grooves inits upper and lower surfaces which reduce contact friction with therespective central facing surfaces of the upper and lower casings. 23.The ring bearing of claim 22, further comprising additional grooves orrecesses in the upper and/or lower surfaces of the plastic ring whichfurther reduce contact friction with the respective facing surfaces ofthe upper and lower casings.
 24. The ring bearing of claim 17, whereinsaid plastic ring has lateral grooves or recesses capable of holdinglubrication.
 25. The ring bearing of claim 17, wherein upper and lowerfacing surfaces of said plastic ring respectively engage said upper andlower casings at corresponding lower and upper facing surfaces thereof.26. The ring bearing of claim 25, wherein said respective facingsurfaces of said casings and said ring are engaged primarily at centralportions thereof.
 27. The ring bearing of claim 26, wherein saidrespective facing surfaces are curved, said facing surfaces of said ringhaving at least in part a smaller radius of curvature than said facingsurfaces of said casings.
 28. The ring bearing of claim 26, wherein saidrespective facing surfaces are curved, said facing surfaces of said ringhaving at least in part the same radius of curvature as said facingsurfaces of said casings.
 29. The ring bearing of claim 25, wherein saidrespective facing surfaces of said casings and said ring are engagedprimarily at inner and outer portions thereof.
 30. The ring bearing ofclaim 29, wherein central portions of said facing surfaces of saidplastic ring are spaced away from the corresponding facing surfaces ofthe upper and lower casings.
 31. The ring bearing of claim 29, whereinsaid inner and outer portions of said ring and said casings are at leastpartially curved with the same radius of curvature.
 32. The ring bearingof claim 25, wherein said respective facing surfaces of said ring andsaid upper and lower casings are at least partially flat.